What version of UG are you using? Are you exporting an image of your model, of a rendering, of a drawing or what? There are several things that can be exported as tiff images, but not all methods are the same.
If on a Windows platform, just hold down the Alt key & hit Print Screen. Open up your image viewing/editing software (like M$ Photo Editor or Irfanview) and then Paste (Ctrl + V) and save as a tiff.
As far as I know, there is no control over the image orientation in UG when using the File -> Export -> Tiff route.
